Communication networks, and particularly wireless communication networks, operate by sending information between base transceiver stations (“BTS”) and base station controllers (“BSC”). FIG. 1 is an illustration of a wireless communication network 100. The wireless communication network 100, in this particular illustration, relates to cellular telephone or mobile stations 102, but it will be understood that other types of data communication devices could be substituted for mobile stations 102. The mobile stations 102 establish wireless communications links 104 to the BTS 106. Conventionally, BTS 108 is connected to BSC 112 using wired communication links 110, such as, for example, T-1 lines, T-3 lines, E line equivalents, or the like.
In operation, mobile stations 102 transmit information to BTS 108 over the wireless communications link. BTS 109 packages the received information from the mobile stations into packets pursuant to a transmission protocol, and transmits each packet to BSC 112 using conventional protocols. Commonly, BTS 108 organizes the information into a frame of information that is transmitted over a communications link which can run asynchronous transfer mode. When ATM communications links are used for transmission, the BTS 108 and BSC 112 will support ATM protocol or an interworking gateway will be used to provide the translation of the packets into the ATM communications link. Prior to transmitting the information over the ATM communications link, it is organized into one or more cells. Thus, for each packet from a mobile station 102, there may be one or more corresponding cells. The cells are transmitted with a plurality of other information to BSC 112 over the ATM communications link. The BSC 112 extracts the frames of information from the ATM communications link and distributes it as required to local or remote end points (not specifically shown, but generally known in the art).
When transmitting information over an ATM communications link, it is necessary to convert the frames of information into packets that may be then sent across the ATM communications link. Segmenting the packets into cells of information for transmission across an ATM network, and the reception of the cells from an ATM network, is well known and is referred to as segmentation and reassembly (SAR) of ATM data. Commonly, ATM network components have what's referred to as ATM adaptation layers which perform segmentation and reassembly functions. There are a number of different types of ATM adaptation layers and such ATM adaptation layers are well known in the art. Several ATM adaptation layer protocols have been defined by the international telecommunications union, including ATM adaptation layer protocol (AAL) types 1-5, which are classified based on whether any particular timing relationship must be maintained between source and destination locations, whether applications require a constant bit rate and whether the transfer is connection oriented or connectionless. ATM adaptation layer 5 (AAL5) is commonly used to send variable link packets up to 65,535 octets in size across an ATM network. AAL5 is one adaption type that is commonly used to transmit data between BTS 108 and BSC 112.
When an application sends information over an ATM connection using AAL5, the sending function typically delivers an entire block or packet of information to an AAL5 interface. The AAL5 interface generally appends an 8 octet trailer to the block or packet information, divides the provided information into a number of different pieces, each piece having 48 octets of data. The AAL5 interface then transfers each of the 48 octet pieces across the ATM network in a single ATM cell. On the receiving end of the connection, the AAL5 interface reassembles the incoming cells into a packet, checks for errors in the packet and provides the resulting block of information to other functions on the receiving end of the ATM network. The process of dividing a block of information into cells, and regrouping them into a packet, is known as ATM segmentation and reassembly (SAR). An AAL5 interface, as can be seen, must receive the information, segment the information, and generate the appropriate error checking information to be sent along with the information in the ATM cells. In some cases, the AAL5 interface must wait for a significant period of time to receive all of the information that is to be transferred over the ATM network. Accordingly, it would be beneficial in many cases to reduce the amount of delay between when the information is first received at the AAL5 interface and when the information may be sent.